1. Field
The disclosed subject matter relates to a hydrogen or oxygen electrochemical pumping catalytic membrane reactor, whose purpose is to increase the conversion and/or the selectivity of hydrogenation, dehydrogenation, deoxidation and oxidation reactions, both in liquid or gas phases.
The disclosed subject matter also relates to the use of a hydrogen or oxygen electrochemical pumping catalytic membrane reactor for the direct amination of hydrocarbons, particularly for the conversion of benzene into aniline, by reacting it with ammonia.
2. Related Art
The use of electrochemical pumping of hydrogen or oxygen is described in the open literature concerning systems related with energy production such as fuel cells. In the case of hydrogen, electrochemical pumping is present in polymeric membrane electrolyte fuel cells or “PEMFC,” wherein the oxidation reaction on the cathode causes hydrogen permeation, under protonic form, from the anode to the cathode. On the other hand, in solid oxide fuel cell or “SOFC,” the electrochemical reaction causes ionic oxygen to go from the cathode to the anode.
The literature also describes chemical reactions that may be undertaken with advantage in reactors with electrochemical pumping of hydrogen or oxygen. These systems are known as electrochemical membrane reactors and are described generally, for example in Marcano, S. and Tsotsis, T., “Catalytic Membranes and Membrane Reactors”, Wiley-VCH, Chapter 2, 2002. However, it was never considered before the use of said reactors for the direct amination reactions of hydrocarbons and namely the direct amination reaction of benzene to aniline.
This direct amination reaction of benzene was first proposed in 1917 by Wibaut, as mentioned in, for example, Dialer, H.; Frauenkron, M.; Evers, H.; Schwab, E.; Melder, Johann-Peter; Rosowski, F.; Van Laar, F.; Anders, Joachim-Thierry; Crone, S.; Mackenroth, W.; Direct amination of hydrocarbons. U.S. Patent Application Publication No. 2008/0146846 A1, 2008. Ever since, many efforts have been developed to improve the conversion rate of this reaction, which is limited by the thermodynamic equilibrium.
U.S. Patent Application Publication No. 2009/0023956 describes several advances achieved. One of the most successful approaches was achieved by Dupont, whose description can be found in Documents U.S. Pat. No. 3,919,155, U.S. Pat. No. 3,929,889, U.S. Pat. No. 4,001,260 and U.S. Pat. No. 4,031,106, revealing the use of a Ni/NiO catalyst, wherein structural oxygen is used to oxidize the hydrogen formed. Both the catalyst and the process, however, present difficulties as far as the catalyst regeneration is concerned, as well as the maximum conversion that can be achieved is lower than 13% when working at 300° C. and 300 bars.
More recently, U.S. Patent Application Publication Nos. 2009/0023956 and 2009/0203941 generally disclose the addition of oxidizing gases to the reactor and the use of a suitable catalyst for the internal oxidation of hydrogen to water. Those publications also generally describe the use of a catalytic membrane reactor with a palladium or a palladium alloy membrane to carry out the direct amination reaction of benzene. A process is described, wherein hydrogen is removed from the reacting medium owing to the partial pressure difference between the retentate side (reacting medium) and the permeate side, wherein a sweep gas current is applied. This system enables the improvement of the benzene to aniline conversion up to 20% of conversion.